Pipelines used for recovery and transport of fluid or gas generally include many pipe segments joined together in an end-to-end configuration to extend a distance of transport. For example, pipe segments may be joined together to extend up to tens or hundreds or thousands of miles.
Pipelines in the oil and gas industry may be used to transport recovered hydrocarbons, such as crude oil, natural gas, produced water, fracturing fluid, flowback fluid, or other types of gas such as CO2, which may be pumped through the pipeline at a selected flow rate. During transport of crude oil, dissolved waxes found in crude oil can precipitate and build up when subjected to temperatures below or equal to a temperature referred to as the “wax appearance temperature” (WAT) or the “cloud point.” The cloud point is specific to each crude composition, and is a function of wax concentration, the concentration of nucleating agents such as asphaltenes and formation fines, and pressure. When enough wax has built up in the pipe, flow of the oil may be restricted, thus reducing efficiency and production. Offshore pipelines are commonly exposed to colder temperatures, and thus, techniques, such as pipe insulation, are implemented to inhibit buildup of wax found in the crude oil. To monitor integrity of the offshore pipelines and clean deposits that have built up within the pipelines, devices know as “pigs” are often sent through the pipelines. For example, some pigs may be used to detect damage to the pipeline, such as dents, corrosion, or cracking.
Onshore pipelines may also be inspected for mechanical damage using pigs. However, as onshore pipelines run above ground and more commonly are buried a few feet below the ground, pipe integrity may also be monitored by walking along the path of the pipe or tubular conduit with various sensing equipment, such as acoustic emission tools, to detect any failure.